1. Field of the Invention
The present invention relates to a computer test method, and more particularly to a method for testing noise of a record/play-back loop in a computer audio system. The method comprises the steps of: (a) the FM synthesizer outputs a sinusoidal analog signal to the output device via the mixer; (b) the analog signal is outputted to an input device via a connection element and then is outputted to the A/D converter for being converted to a digital signal which further stored as a digitized audio document; (c) the system performs a mathematical analysis on the audio document in order to calculate a signal-to-noise (S/N) ratio and a signal distortion of the record/play-back loop; and (d) the S/N ratio and the signal distortion described in step (c) are compared with a pair of predetermined standards respectively in order to determine that whether the S/N ratio and the signal distortion meet the predetermined standards.
2. Background Information
Conventionally, the sound of a personal computer (PC) speaker is monotonous. However, the emergence of computer audio system has completely change that. It can play easy listening music and even produce various sound effects to let consumers enjoy realistic sound.
It is known that a good audio system is a must for upgrading an ordinary PC to a PC with multimedia feature. Therefore, many potential computer buyers view a PC with a good audio system as a top selection priority. It is also known that an analog to digital (A/D) converter of the computer audio system is the most important device for recording or playing sound and music.
It is found that a poor A/D converter is blamed for disharmonious sound as well as for the distortion of original sound effect recorded. This is quite not desirable for a computer consumer. Accordingly, the manufacturer conducts a series of tests on the A/D converter as a part of the quality control process for judging the goodness of recording and playing features of the A/D converter. The most important test of them is the test on the A/D converter. Traditionally, the A/D converter test is conducted in either way:
(a) Manually conducted by a test person, i.e., the test person judges the sound quality of the tested A/D converter by ear, but this is unsatifactory for the following reasons:
1. Relies on experiences and personal judgment of the test person and thus quite unreliable due to personal factors; PA0 2. There is no common test rule and thus test results between two persons sometimes are different, i.e., the deviation is too large and unacceptable; or PA0 1. The test procedure is time consuming; PA0 2. A trained test person is required; PA0 3. The cost is higher.
(b) Use an oscilloscope that visually display an electrical wave of the tested A/D converter, but this is unsatifactory for the following reasons:
Thus, it is desirable to provide a method for testing noise of a record/play-back loop in a computer audio system with the advantages of being objective, repeatable, adjustable, convenient, time saving and cost saving.